Reinforced headbox for paper machine



W. C. NOTBOHM REINFORCED HEADBOX FOR PAPER'MACHINE Filed June 14, 1967 Sept. 15, 1970 FIG-1 22 23 //V VEN TOR WILLARD C. NOTBOHM ATTORNE- FIG- United States Patent O REINFORCED HEADBOX FOR PAPER MACHINE Willard C. Notbohm, Watertown, N.Y., assignor to The Black Clawson Company, Hamilton, Ohio, a corporation of Ohio Continuation-impart of application Ser. No. 384,640,

July 23, 1964. This application June 14, 1967, Ser. No.

The portion of the term of the patent subsequent to June 27, 1986, has been disclaimed Int. Cl. D21f 1/02 US. Cl. 162-342 5 Claims ABSTRACT OF THE DISCLOSURE A paper machine headbox assembly especially adapted for use as a secondary headbox incorporates a multiple tube assembly unit which connects the stock supply chamber with the slice assembly and which serves also as the main structural element for reinforcing the headbox assembly and supporting the slice lip assembly with respect to the forming wire of the paper machine. A stock supply header is built into the headbox so that it also functions as a structural element as well as a header.

CROSS REFERENCES TO RELATED APPLICATIONS This application is a continuation-in-part of my appli cation Ser. No. 384,640, filed July 23, 1964, now Pat. No. 3,328,237. Cross reference is also made to the copending application of William H. Burgess, Jr. and Girard L. Calehuif, Ser. No. 376,699, filed June 22, 1964, now Pat. No. 3,328,236 and assigned to the same assignee as this application.

BACKGROUND OF THE INVENTION A secondary headbox for a Fourdrinier paper machine is utilized to apply a layer of paper making stock on top of the layer previously applied to the wire by the primary headbox. The secondary headbox is therefore supported at its ends above and in spanning relation with the Wire, and for optimum results, the slice lip assembly and the supply passage thereto should be kept as uniform and as straight as possible. The loads and stresses effective on the headbox in use produce a definite tendency toward sagging, particularly on paper machines of substantial width, and it is difiicult with conventional prior art constructions to obtain sufficient reinforcement to overcome these loads and stresses.

The parent application of which this case is a continuation-in-part discloses a headbox assembly wherein the stock supply chamber is connected with the slice assembly by means of a tube assembly unit defining a plurality of separate and parallel passages of relatively small individual cross-sectional flow area for delivering the stock from the supply chamber directly to the outlet passage defined by the slice lips.

The present invention is particularly concerned with the provision of a secondary headbox assembly incorporating a similar multiple tube assembly unit which not only performs the stock supply function noted above, but which also serves as the major structural element for reinforcing the headbox assembly, particularly in the vicinity of the slice assembly, in order to maintain uniformly straight discharge flow conditions across the entire width of even a relatively wide paper machine.

SUMMARY OF THE INVENTION The present invention provides a headbox assembly which is especially adapted for use as a secondary headice box because of the high degree of rigidity which it achieves in those portions of the headbox establishing the discharge flow conditions of stock onto the wire. More specifically, the headbox of the invention incorporates a stock supply chamber and a slice assembly which are interconnected by a multiple tube assembly unit composed of separate and generally parallel passageways of relatively small individual cross section which are rigidly secured together in such manner as to establish a beam-like structure.

The tube assembly unit in the secondary headbox of the invention has essentially the same operational function as in the above parent application in that it establishes essentially uniform flow distribution of the stock to the slice assembly. It accomplishes this function by its controlling effect on the stock flow therethrough, but in addition, it possesses sufliciently high physical strength and rigidity to resist the stresses and loads which tend to produce sagging and variable flow areas in the cone sponding portions of conventional secondary headboxes. Thus it forms the major structural reinforcing element of the headbox for supporting the slice lip assembly itself, and assures that there will be minimum sagging and/ or variation of the slice lip opening even on a headbox which must span a forming wire of substantial width, such as 300 inches or more.

Another distinguishing characteristic of the secondary headbox of the invention, particularly for use on relatively wide paper machines, lies in the novel manner in which the cross flow supply header for furnishing the stock to the supply chamber serves also as a supplemental reinforcing and supporting element for the headbox assembly as a whole. In particular, the invention provides a secondary headbo'x wherein the cross flow header is directly supported on the tube assembly unit, and a Wall common to the header and to the supply chamber is provided with perforations through which the stock flows into and through the supply chamber to the multiple passageways of the tube unit. On headboxes for wide paper machines, the piping connected to the supply header also provides a supporting function for the headbox as a whole.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a view generally in vertical section showing a secondary headbox constructed in accordance with the invention and mounted in operative relation above the forming wire of a Fourdrinier paper machine;

FIG. 2 is an enlarged fragmentary section on the line 2-2 of FIG. 1;

FIG. 3 is a view similar to FIG. 2 showing a modified construction of the tube unit;

FIG. 4 is a view similar to FIG. 1 showing another form of headbox in accordance with the invention;

FIG. 5 is a view similar to FIG. 1 showing still another form of a headbox in accordance with the invention;

FIG. 6 is an enlarged fragmentary section on the line 66 of FIG. 5;

FIG. 7 is a fragmentary view showing a modification of the headbox of FIG. 5; and

FIG. 8 is a view similar to FIG. 2 showing a third modification of the construction of the tube unit.

DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 shows the headbox assembly 10 positioned as a secondary headbox above a fragment of the forming wire W of a Fourdrinier paper machine on which there is assumed to be a layer of fiber previously applied thereto from a primary headbox. The headbox assembly 10 comprises four main components, which are the crossflow stock supply header 11, the supply chamber 12, a tube assembly unit 13 defining a multiplicity of small parallel passages leading from chamber 12, and the slice assembly 15 which receives the stock from the tube assembly 13 and delivers it to the forming wire.

The supply chamber 12 extends the full width of the wire and is in essence a box of generally rectangular outline in horizontal section defined by vertical front and back walls and 21 and end walls 22. A top wall 23 encloses chamber 12 so that it can be pressurized if desired, as indicated by the air inlet connection 24. The bottom wall 25 of chamber 12 is cylindrically curved about an axis located within the chamber and extending parallel with wire W, and a rotor 26 is mounted by shaft means 27 for rotation in chamber 12 on the axis of curva ture of bottom wall 25.

The tube assembly unit 13 is shown in detail in FIG. 2 as comprising a multiplicity of individual cylindrical tubes 30 brazed or otherwise secured together at 31 in closely packed parallel relation to define a honeycomb arrangement in section. In accordance with the invention, the individual tubes 30 are of small cross-sectional flow area, namely of the order of 0.25 inch to 1.00 inch in inner diameter, to provide a corresponding plurality of small parallel flow passages, and preferred results have been obtained with tubes having an inner diameter of 0.50 inch. It is not essential however, that individual or cylindrical tubes 30 be used, and FIG. 3 shows a modfied equivalent construction composed of multiple corrugated sheets 33 secured together to provide a honeycomb arranegment of small parallel flow passages 35. Additionally, FIG. 8 shows a third modified construction wherein a solid block of material is drilled to provide passages 36. Accordingly, references herein to tubes in connection with the assembly unit 14 and corresponding units in other views are to be understood as including such modified constructions which meet the other requirements of the invention as described herein.

The major function of the rotor 26 is to create multiple eddy currents of small magnitude in the stock immediately adjacent the inlet ends of the tubes 30, for the dual purpose of minimizing flocculation in the stock and preventing clogging or plugging of the tubes, as a result either of flocculation, the presence of lumps in the stock, or stapling of fibers around the edges of the tubes. The rotor 26 should therefore have a discontinuous periphery in order to create pulsations adjacent the inlet ends of the tubes 30, and for optimum results the inlet end surface 37 of the tube unit should be cylindrically curved on the same center as the axis of rotor 26 to form a surface generally parallel to the periphery of the rotor, and the periphery of the rotor should travel in closely spaced relation with the curved surface 37, this spacing being only sufilcient to assure running clearance and preferably being not more than inch.

The tube assembly unit 13 serves as the major structural element for reinforcing the headbox assembly 10, due primarily to the fact that its honeycomb construction gives it sufliciently high strength and rigidity to maintain itself essentially straight and horizontal while supporting the associated parts of the headbox assembly and the internal stresses incident to its use. It is particularly effective in maintaining the slice assembly 15 in the desired straight condition during operation to assure uniform dscharge flow conditions of the stock onto the wire. When the headbox assembly 10 is therefore in use as a secondary headbox, it is desired to connect the ends of the unit 13 directly to the frame means by which the headbox assembly is supported on the floor in operative position with respect to the forming wire.

As noted, the slice assembly 15 is primarily supported by the tube assembly unit 13, and it comprises upper and lower wall members 40 and 41 clamped, welded or otherwise secured to the tube assembly unit 13 and converging forwardly and downwardly therefrom. The lower slice lip 42 is secured to the forward end of the lower wall memher 41 and a brace 43 connected at its other end to the chamber 12. The upper slice lip 44 is provided with a hinged mounting 45 extending along the forward edge of the upper wall member 40.

A brace 49 is connected between the hinge 45 and a plate-like beam 50 which extends the full length of the headbox assembly and is secured at opposite ends to conventionally located plates 51. This beam 50 forms a support for the member 52 which carries the adjusting screws 53 for the upper slice lip 44, and which is adjustable on the beam 50 by means of a plurality of jacks 55 as shown. A plate 56 extends upwardly from the beam 50 and may be connected as indicated at 57 to suitable supporting structure extending between the end frames which are mounted on the floor. A plate 58 is connected between the plate 56 and the front chamber wall 20 to serve both as a footwalk and as an additional brace.

The crossflow header 11 is also a significant structural part of the headbox assembly 10 in addition to its function of serving as the stock supply manifold for the chamber 12. The wall 60 is common to both the header 11 and chamber 12, extends the full length of the wire, and is provided with multiple perforations 61 for admitting stock from the interior of header 11 to chamber 12. The header 11 is rectangular in cross-section and is preferably tapered lengthwise for increased uniformity of fluid pressure throughout its length, with its wall 62 converging toward perforate wall 61 in the direction of stock flow through the header.

The four walls of the header 11 are readily made of sufficiently heavy material to impart substantial rigidity to the headbox assembly as a whole and thereby to facilitate its mounting in suspended position above the forming wire, and the supply connection to the inlet end of the header and the overflow connection at its smaller end contribute to the supporting mounting of the headbox assembly as a whole. Additional reinforcing cooperation is obtained with the bottom wall 63 of the header flat and fitting directly against the upper surface of the tube assembly unit 13, and if desired, these parts can be directly clamped together as indicated by the bolt and nuts 65.

As already noted, the rotor 26 serves two functions in use, one being to keep the face of the tube assembly clean, and the other being to create sufiicient turbulence in the supply chamber for maintained defloccnlation. The peripheral speed of the rotor should be such that its discontinuous portions move past the inlet and into the tube assembly at a frequency such that the individual impulses are substantially blended by the time the stock reaches the forming wire. This result is further contributed to by the overall design of the headbox, and particularly by the fact that the tube assembly effectively isolates the slice outlet from the effects of the high energy input in the supply chamber.

It is important for maximum uniformity of sheet formation that the eddy currents created at the inlet end of the tube unit by the rotor 26 have sufiicient time to decay before the stock is deposited on the wire, but this time interval should not be of such length that the distribution characteristics imparted to the stock in the chamber 12 have the opportunity to deteriorate. This time interval is a function of the velocity of the paper machine and therefore the velocity of flow of the stock from the chamber 12 to the slice lip assembly 15, and the distance traversed by this flow is preferably established to provide the desired time interval in accordance with the flow velocity.

For preferred results, from the standpoint of the factors just discussed, tests indicate that the. flow velocities through the successive sections of the headbox should be in the range of conventional paper machine flow velocities, and particularly that they should not materially exceed the velocities conventionally used for a given paper machine speed. For example, if the wire speed is 950 feet per minute, preferred results are obtained in conventional practice if the velocity of the stock as it enters the larger end of the outlet passage 64 is of the order of 1 to 2 feet per second. For the same wire speed, preferred results are obtained in the practice of the invention if the tube assembly unit 13 has approximately /2 as much effective flow area as the larger end of the passage. defined by walls 40 and 41 into which it discharges. In other words, the tube assembly 13- should provide approximately 50% open area so that the flow velocity therethrough is approximately twice that in the larger end of the outlet passage, and the velocity of the multiple separate streams of stock through the tubes is therefore decelerated by approximately 50% as these streams merge in the larger end of the outlet passage and are then again accelerated as they approach the outlet slot defined by lips 42 and 44.

The figure of 50% as used in the preceding paragraph does not appear to be critical but rather an approximate value. As illustrative of the range which the 50% figure typifies, for a wire speed of 1300 feet per minute, satisfactory results have been obtained with a flow velocity through the tubes of 7.5 feet per second which dropped to 3.0 feet per second at the larger end of the outlet passage. For a wire speed of 1500 feet per second, the comparable figures are 8.6 and 3.5 feet per second. It will also be apparent that these figures will vary for different basis weights at the same wire speed, but the ratio of velocity in the tubes to the velocity at the larger end of the outlet passage will remain of the same general order.

The length of the individual tubes in the tube assembly unit 13 does not appear to be critical but does have practical limitations. For example, these tubes should be long enough for the pulsations of the rotor 26 to die out and for the multiple streams to assume parallel fiow characteristics. Each of the individual tubes should therefore have a length which is at least six times its inner diameter, but there appears to be no theoretical reason for materially increasing the lengths of the tubes beyond this value, and satisfactory results have been obtained with the individual tubes of /2 inch inner diameter and with the unit 13 approximately 12 inches in length.

The tube assembly 13 is advantageously constructed of multiple individual tubes or sheets brazed together as described to form a rigid honeycomb structure. Comparable results in operation can be obtained if this section of the assembly is fabricated by drilling a solid block of metal or suitable plastic so long as the other requirements discussed herein are met. One of the major advantages provided by this construction derives from its strength in vertical section, particularly as compared with a conventional open slot or throat connection to the slice, which renders both itself and the slice lips subject to distortion in withstanding the substantial pressures of the headbox under conditions of high speed paper machine operation. In contrast, the honeycomb section of the invention assures constant effective flow area to the slice across the entire width of the paper machine.

The headbox assembly .10 is practical for use as a primary headbox, but it offers special advantages as a secondary headbox because of its comparatively simple and lightweight but strong and rigid construction. The

tube assembly 13 contributes multiple advantages in a secondary headbox apart from its major function in delivering stock to the slice, especially from the standpoint of the great strength which it has in vertical section as compared with a conventional open slot or throat connection to the slice, and which further contributes to uniformity of sheet formation by assuring that the effective flow area from the supply chamber to the slice assembly will remain uniform across the entire width of the machine under all pressure and speed conditions.

FIG. 4 shows another form of headbox assembly 70 in accordance with the invention which is in some respects similar to the assembly and is also especially adapted for use as a secondary head-box. The tube assembly unit 71 in FIG. 4 is somewhat L-shaped in section but otherwise corresponds in structure and function to the unit '13, and it similarly conducts stock to the slice assembly 72 from the supply chamber 75 having therein a perforated roll 77 which corresponds in location and function to the rotor 26. The lower slice lip 80 is supported by and projects from the lower casing member 81 of the tube assembly unit 71. The inclined upper slice lip 82 has its hinged mounting 83 on the forward end of the upper casing member 84 of tube assembly unit 71.

Advantage is taken of the L-shape of tube assembly unit 71 to provide support for the supply header 88-, which is supported in part by the casing member 84 and communicates with the bottom of supply chamber 75 through a common perforated wall 89. A hollow beam assembly 90 extends the full length of the headbox immediately forward of the header 88, and its front wall forms the support for the adjusting screws 91 for the upper slice lip 82, these screws being carried by a beam 94 which is adjustably mounted on the beam 90 by jacks 95 as shown.

The headbox assembly 70 offers advantages similar to the headbox 10 for use as a secondary headbox and it is also similarly usable as a primary headbox. Its tube assembly 71 offers comparable advantages of strength in supporting a substantial portion of the weight of the assembly, and it also demonstrates that it is not essential to the invention that the tube assembly be straight.

FIGS. 5 and 6 show another form of secondary headbox assembly which is generally similar to the headbox assemblies 10 and 70 in comprising as main components, a cross flow supply header 101, a supply chamber 102, a tube assembly unit 103, and a slice assembly 105. The chamber 102 has a cylindrically curved bottom portion 106 which is connected with the unit 103, and a rotor 107 is mounted for rotation in chamber 102 concentrically with the curved wall portion 106.

The tube assembly unit 103 is of individually different construction from those previously described, and it comprises multiple individual tubes t110 of cylindrical section spaced from each other in the pattern shown in FIG. 6 and connected at their opposite ends to end plates 111 and 112 of relatively heavy section. Satisfactory results have been obtained with individual tubes 110 having an outer diameter of .675 inch and a wall thickness of .028 inch, and with the end plates 111 and 112 each of a minimum thickness of 1 inch, the inner end plate 111 being of varying thickness due to the fact that its end surface facing the chamber 102 is cylindrically concave on the same center and radius as the curved chamber wall portion 106. The tubes 1.10 are readily secured to the plates 111 and 112 by expanding the ends of the tubes tinto correspondingly sized and aligned holes in the plates, and top and bottom cover plates 114 and 115 are welded or otherwise secured to the edge surfaces of the end plates .111 and 112.

The head-box construction shown in FIG. 5 is partioularly suitable for paper machines of relatively narrow width, such as within a range of 100 inches. For such headboxes, the tube unit 103 provides such substantial reinforcement and support for the slice assembly that it is unnecessary to place significant reliance on the header 101 for reinforcement. It is accordingly shown as a tubular tapered pipe mounted on and connected with the front wall of the chamber 102 by multiple inlet tubes 118.

The slice assembly 105 is of essentially the same construction already described in connection with FIG. 1. The lower slice lip is welded or otherwise secured to the forward lower end of the tube assembly unit 103 and has a suitably braced connection 121 to the rear wall of the supply chamber 102. The upper slice lip 122 has a hinged connection 123 on the forward upper end of the tube assembly 103, and a wall 125 forms a bracing connection extending upwardly from the hinge 123 to a combination upper wall and footwalk 126. The assembly 130 which supports the adjusting screws 131 for the upper slice lip is mounted on the wall 125 for adjustment by means of the jacks 132.

FIG. 7 shows a fragment of a headbox of the same construction as that in FIGS. -6 with the exception that it embodies a cross flow supply header 140 arranged similarly to the headers in FIGS. 1 and 4, in that it is supported on and in reinforcing relation with the tube unit 103 and has a perforate wall 141 common to itself and the supply chamber 102. The headbox construction of FIG. 7 is accordingly particularly well adapted for use as a secondary headbox on a relatively wide paper machine where the additional reinforcing and supporting action provided by the header in combination with the tube unit has advantages in resisting any tendency of the headbox assembly as a whole to sag between its supported ends.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.

What is claimed is:

1. A headbox comprising:

(a) means defining a chamber connected to extend transversely of a papermaking machine,

(b) a stock supply header,

(0) means interconnecting and providing fluid communication between said chamber and said stock supply header,

(d) a slice assembly including a pair of slice lips converging toward each other in a direction toward the forming section of said papermaking machine and defining a stock discharge outlet for directing papermaking stock to said forming section,

(e) a tube assembly unit providing reinforcement for said headbox and inlcuding a pair of spaced, relatively thick plates having aligned holes therein and a multiplicity of tubes having their opposite ends received in said holes,

(f) one of said plates being secured to said chamber with the holes in said plate in communication with said chamber,

(g) the other of said plates being secured to said slice assembly with the holes in said other of said plates in communication with said stock discharge outlet, and

(h) a rotor mounted in said chamber adjacent said one of said plates.

2. A headbox comprising:

(a) means defining a chamber connected to extend transversely of a papermaking machine,

(b) a stock supply header extending coextensively with said chamber,

(0) said chamber and said stock supply header having a common perforated Wall to place said chamber and said stock supply header in fluid communication.

(d) a slice assembly including a pair of slice lips converging toward each other in a direction toward the forming section of said papermaking machine, and defining a stock discharge outlet for directing papermaking stock to said forming section,

(e) means defining a plurality of relatively small passages extending from said chamber to said discharge outlet,

(f) said passages defining means and said stock supply header extending transversely of said papermaking machine in contiguous and reinforcing relationship to each other, and

(g) a rotor mounted in said chamber adjacent said passage defining means.

3. A headbox as defined in claim 2 wherein said passage defining means comprises a plurality of separate tu-bes secured together over at least the major portion of their length to define a generally honeycomb structure.

4. A headbox as defined in claim 2 wherein said passage defining :means comprises a solid block of material having a plurality of openings formed therein.

5. A headbox as defined in claim 2 wherein the end of said tube defining means connected to said chamber is curved to form a surface generally parallel to the periphery of said rotor.

References Cited UNITED STATES PATENTS 3,328,237 6/1967 Notbohm 162347 XR S. LEON BASHORE, Primary Examiner R. H. TUSHIN, Assistant Examiner U.S. Cl. X.R. 162343, 347 

